It is a common practice in the construction of structures to ventilate gable roofs by providing a vent along the roof ridge. Ventilation apertures are formed in the construction process by leaving or cutting an open slot along the ridge through the sheathing material covering the roof. Heated air rises and escapes at the ridge taking with it moisture that may have accumulated within the roof. The flow of wind over the ridge of the roof assists in the extraction of moisture and heated air by creating a zone of relatively reduce pressure as it crosses the ridge. Soffit vents enable the entry of fresh exterior air into the roof to replace air that has left through the ridge vent. Soffit vents are openings in the soffit material covering the undersides of the overhanging eaves of the roof.
Ideally, a ventilated roof provides for an unrestricted outflow of air through the ridge vent and inflow through the soffit vents. However, without protection of the ventilating openings, wind blown precipitation, debris and insects enter the roof and encourage damage to the structure through mildew, rot and infestation. A ventilated cap is therefore placed over the open slot in the ridge and attached to the roof along each side.
Therefore, many types of vent caps have been developed in an effort to provide free flow of air while excluding rain, snow and insects. Louvers, baffles and screens have been standard features of roof vents for decades.
Snow, in particular, is a great concern. It has a small particle size and is lightweight. Wind can carry snow upward and into roof vents readily. Snow particles may bypass louvers and deflectors that prevent the entry of most rain. As much as two feet of wind driven snow has been reported to have passed through roof vents and accumulated inside roof structures.
A number of ridge vent caps employ filtering material to restrict the entry of precipitation and foreign matter. Filtering materials include porous foams and fibrous materials. Examples of the use of porous foams include U.S. Pat. No. 5,830,059 issued to Sells, U.S. Pat. No. 5,673,521 issued to Coulton et al. and U.S. Pat. No. 4,876,950 issued to Rudeen. Both closed cell foams and open cell foams have been utilized. Open cell foams have the benefit of allowing greater airflow but tend to absorb a substantial amount of water. Closed cell foams absorb little water but restrict airflow to a greater degree. Foam products, in general, tend to deteriorate with age and exposure to the elements.
Fibrous materials enjoy wider use as roof vent filters. Examples include U.S. Pat. No. 5,902,432 issued to Coulton et al., U.S. Pat. No. 5,830,059 issued to Sells, U.S. Pat. Nos. 5,561,953, 5,425,672, 5,352,154, 5,167,579 all issued to Rotter. These patents and others disclose the use of mats of randomly aligned synthetic fibers to exclude vermin and the elements from roof vents. The Rotter patents disclose roof vents made entirely from mats of randomly aligned synthetic fibers. Fiber mats may suffer from compression, for example, under a snow load, and add expense and complexity to the construction of roof vents.
Another approach to preventing the entry of precipitation and foreign matter into vents is to employ check valves structured to close at a predetermined wind speed so as to stop the inflow of air and precipitation. Check valves have moving parts and are prone to the possibility of wear and blockage and when they operate ventilation is restricted. They also complicate the manufacturing process. U.S. Pat. No. 5,803,805 to Sells discloses a check valve ridge vent.
In recent years the use of corrugated plastic sheet materials to manufacture roof vents has presented to the marketplace a variety of inexpensive, strong, durable ridge vents which may be applied in sections or as a continuous roll. Ridge vents of this type are typically applied along the peak of a roof and covered by a row of shingles. They are thus referred to as “shingle over roof vents.” Some have sufficient structural integrity such that they can be fastened to the roof with a pneumatic nail gun without crushing the vent.
Examples of corrugated plastic ridge vents include U.S. Pat. No. 5,651,734 issued to Morris, U.S. Pat. No. 5,934,995 to Morris, Kasner and Stoll and U.S. Pat. No. 5,947,817 to Morris, Gosz and Stoll which are incorporated herein in their entirety by reference.
Wind deflectors are sometimes installed along with the vent in order to restrict the entry of rain and snow into the vent. The installation of wind deflectors requires an additional step in the installation process with an attendant increase in time and expense.
The applicant is aware of a single example of a corrugated ridge vent employing a filtering material to exclude precipitation and the like. U.S. Pat. No. 5,704,834 issued to Sells discloses the use of a flexible, air permeable, moisture repelling, woven or nonwoven fabric covering the outer side of the vent passages to resist the penetration of moisture into the vent passages. The fabric filter is held in place by a perforated metal flashing attached either to the roof or to the vent.
Considerable complexity is added to the manufacturing process in order to incorporate the flashing into the vent. The presence of a rigid or semi rigid flashing may also prevent or complicate the rolling of the vent for transport and reduce ease of application. Additionally, the filtering fabric is exposed to the elements. Sun and wind may accelerate its deterioration.
It would be desirable to produce a ridge vent of folded corrugated plastic construction that effectively excludes wind blown precipitation and other foreign matter. The process of manufacturing the ridge vent should be as simple as possible. It would be preferable for such a ridge vent to require no flashing to support the filtering material. The ridge vent would ideally be possible to produce either in a continuous roll or in discrete sections. It would be preferable that filtering material be protected from exposure to the elements to maximize its life.